Transmitters can be built using Josephson junctions created by natural anisotropies in copper oxide-based high temperature superconductors. These anisotropies create stacks of conducting planes separated by insulating regions that combine to form numerous Josephson junctions. The performance of these transmitters is, however, limited by a material-dependent energy gap that sets a maximum voltage that can be applied across the Josephson junctions without destroying them. The transmitter's performance is further limited by the inherent mismatch of the layered superconducting structure and, in consequence, by its reduced surface area.